The present invention relates to a dual band antenna, and more particularly, to a dual band antenna having a single radiating arm operating at dual frequency bands.
With the current developments in communication technology, many electronic devices need to receive and transmit signals in dual frequency ranges. The electronic devices, therefore, need to have dual band antennas operating in dual frequency ranges. U.S. Pat. No. 6,166,694 discloses a dual band antenna. The conventional dual band antenna includes two radiating arms which are of different lengths and which are capable of being tuned to different frequency bands. However, each radiating arm of the conventional antenna is only resonant at one frequency band. The radiating arms occupy a relatively large space. Furthermore, if an electrical device needs a conventional antenna to operate at multiple frequency bands, the antenna has to have an additional radiating arm for each additional frequency band. These radiating arms must occupy extra printed board space and may result in complex shapes. These multiple radiating arms are also disadvantageous when a designer has to decrease the size of the antenna.
The present invention is directed to an improved dual band antenna having a single radiating arm with a closed loop, which operates at dual frequency bands, which obviates adding extra radiating arms, which prevents occupation of extra space.
A main object of the present invention is to provide a dual band antenna with a single radiating arm for operating at dual frequency bands.
A dual band antenna in accordance with the present invention comprises a printed wiring board (PWB) having opposite first and second surfaces, with an antenna trace disposed on the first surface, and with a grounding plate disposed on the second surface of the PWB. The antenna trace includes a radiating arm and a matching means extending from the radiating arm. The radiating arm includes a meandering segment and a linking segment. The meandering segment includes a plurality of U-shaped bends. The linking segment is provided to short cut one of the U-shaped bends, thereby forming a closed loop. Because of the closed loop, the radiating arm has two transmission paths, one longer path, which does not include the linking segment, and one shorter path, which does include the linking segment. The dual band antenna, therefore, is capable of operating at two different frequency bands along two paths of the single radiating arm.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.